Cable joint



Sept. 14, 1937. N. E. BUCK ETAL CABLE JOINT Original Filed NOV. l2, 1928Patented Sept. 14, 1937 rUNITED STATES PATENT OFFICE 2,093,305 CABLEJonvr Nelson E. Buck and Denney W. Roper, Chicago, Ill., assignors toGeneral Electric Company, Schenectady, N. Y., a corporation of New YorkOriginal application November 12, 1928, Serial No. 318,793. Divided andthis application May 12, 1930, Serial N0. 451,582

1 claim. (ci. 17a-26s) uid dielectric wherein a duct is provided for theCIK dielectric. It is a particular o bject of the present invention toprovide an improved joint between the ducts of adjacent cable sectionsand also an improved connection between the conductors of adjacent cablesections.

Oil filled lcables may be of the single conductor type or of themulti-conductor type. For the highest voltages single conductor cable isrequired. The cable contains a hollow stranded conductor iilled with aninsulating oil which impregnates the paper insulation surrounding theconductor and which lies between the conductor and the enclosing leadsheath.

The oil within the cable must be gas free and great precautions aretaken to prevent the contamination of the oil by air or otherimpurities. The cable as initially installed may be iilled with gas freeoil and maintained under pressure by suitable means, for instance suchas is disclosed in our parent application Serial No. 318,793, filedNovember 12, 1928, or it may be of the type adapted to be firstevacuated and then lled with oil after installation in the conduit. Thecable to be installed is shipped on reels in the usual manner and is ofsuch length as to reach from one manhole or splicing chamber to thenext. After installation of the cable lengths in the conduit the severalconsecutive lengths are connected by joints, the joints being made sothat the oil ducts between the consecutive'cable lengths -or sectionsare continuous. If the cable installed is of the type that is initiallylled with oil it is necessary to prevent too great a loss of oil duringthe time that a joint is being made and to assure the maintenance of agas free condition of the oil in the cable. To achieve this result Weprovide a connector oi' an improved construction for joining the ducts,said connector being provided with a valve which may be closed offduring the making of the connection between the oil ducts.

After the cable is installed it is of course subject to failure or toexternal damage to the lead sheath. In either case, the removal of thelead sheath locally, or the making of any small hole in the sheath, orthe development of a crack in the sheath due todefective workmanship ormaterial at the factory, will provide a `passage through the lead sheaththrough which the oil may ilow. To repair the line it is necessary tofirst determine the location of the ylength of cable in trouble, andthen open up the joints at the two ends of the defective length of cableso as to remove this length. It is also necessary to close off the ductsof the two `cable lengths at the opposite ends of the defective section.If this were done then since the oil in the interior of the cable isunder pressure there would be a tendency 'for the oil to flow fromvopenings in the two adjacent lengths and, unless provision were madeI tothe contrary, air, moisture, or water A would flow into this hollowinterior, damaging the insulation.

It is an object of the present invention to construct a cable joint insuch a manner as to limit the possible consequential damage resultingfrom an injury in a portion of the cable sheath, and

to conne the effect of cutting out and replacingA one or more cablelengths to only the length replaced. The vessence of our inventionresides in making a cable joint in such a manner that the entrance ofair, moisture, or other impurities into the cable is prevented both inthe initial cable installation, in cases where the cables to beinstalled are shipped full of oil, and also in the replacement of adefective or injured section of cable, without permitting a too greatloss of oil in either case. It has been customary to provide a sleevefor connecting the oil ducts of consecutive lengths of cable. It is oneof the objects of the present invention to provide this sleeve with avalve seat into which may be placed a valve for closing off thecommunication between the oil ducts in adjacent lengths. This valve isprovided with a passageway for permitting selective communicationbetween the oil ducts on either side thereof and the outside of thesleeve. This passageway may be used to permit a slight outward flow ofoil for a short while after the making of a joint in cases where thecable section installed is initially illed with oil, or it may be usedfor evacuation purposes in cases where the cable as initially installedis not iilled with oil.

-Prior to the completion of the joint the valve is removed and is'replaced by a tapered plug which is provided with a passageway forpermitting communication between the adjacent oil ducts. Thereafterinsulation is applied to the joint and the joint is completed in theusual manner.

The attainment of the above and further objects of the present inventionwill be apparent from the following specification taken inconjunctionwith the accompanying drawing forming a part thereof.

In the drawing:

Figure 1 is an isometric view of the end of a typical form of cable towhich our improved connector is applicable;

Figure 2 is a longitudinal vertical section of one form o-f permanentjoint employing our connector;

Figure 3 is a longitudinal section of the connector sleeve for joiningthe hollow conductors of the cables shown in Figure 1;

Figure 4 is an enlarged side view of the ported plug used with ourconnector;

Figure 5 is a top plan View of the same;

Figure dis an enlarged view of a valve used while making the joint, orwhile making repairs thereto; and

Figure '7 is a top plan View of the same.

Reference may now be had more particularly to the drawing wherein wehave shown our improved connector applied to a cable joint which isotherwise of a well known construction and forms no part of the presentinvention. The cables joined by this joint are also of a constructionwell known in the art and do not, per se, form apart of the presentinvention. The cable is constructed as shown in Figure 1. It has acopper conductor l which is formed of several layers of strands having ahelical twist, successive layers being twisted in opposite directions,and the inner layer resting on a spiral metallic tape il. `The spiraltape provides an internal passageway or duct through which oil ispermitted to flow, said duct lforming a passageway for the insulating oil to reach all parts of the cable insulation within the lead sheath.The copper conductor l is surrounded with wrapped paper tape insulationl2. This 'paper tape is carefully evacuated and impregnated withinsulating oil. Outside of the paper insulation a suitable sheath orarmor is provided, this comprising a rst lead sheath i3, a wrapping ofhard drawn copper tape lll between layers of impregnated paper, and anexternal lead sheath l so as to present a smooth surface while the cableis being drawn into the conduit. The reason for the reenforcement of thesheath is the high lnternal pressure to which the cable is subjected.Also, a suitable single lead sheath may be used.

Reference may now be had to Figure 2 showing the construction of acablejoint between two cables of the kind shown in Figure 1. In thisgure we have illustrated a joint which is substantially the saine as theGeneral Electric Companys joint, differing therefrom mainly in that wehave introduced a valve between the sections being joined so as topermit the shutting 01T of the oil flow between the sections. YThe valveis located in a connector indicated at 2U which is located between thecable sections being joined. r'I'his connector is of a construction suchas is shown more fully in Figure 3,I to which further reference will behad as the description proceeds. The cable lengths being joined areindicated by the reference numerals I and 2 respectively. The connector28 and the adjacent stepped ends of the cable insulation i2 of therespective cable lengths are wrapped with suitable insulating wrappings25 and 26. Metal tape 2l is wrapped spirally over the tapered ends ofthe insulation 26 at the end, and a divided sheet metal sleeve is joinedat the center by a wiped joint 28, the ends of the sleeve being tapereddown to substantially the diameter of the lead sheath l5 and y plug 39.

joined thereto by wiped joints as indicated at 29 and 3U. The sleeve isindicated by the reference numerals 3l and 3i and the joint is centeredin the sleeve by internal braces 32 resting against an inner insulatingsleeve 33 supported upon blocks of insulation 313 and 35 resting uponthe insulation 26. During the initial laying of the cable and during themaking of repairs upon the cable, especially such repairs as necessitatethe replacement of one of the cable lengths. between adjacent manholes,it is necessary to use a ported plug such as is shown in Figures 6 and7. The connector 2G is provided with a tapered valve seat into which theported plug shown in Figure 6 is adapted to t. When the plug shown inFigure 6 has served its purpose during the making of the repairs it isremoved and the opening in the connector is plugged by a permanent valveIn order to facilitate the making of repairs in the future, the valveseat for the plug Shown in Figure 6 is preferably formed in theconnector 2E) as initially installed, the same being closed by the plug30. It is however Within the purview of our present invention to useconnectors wherein the valve seat is not initially provided. Under suchconditions it would be necessary when making repairs to drill and reamthe connector 2@ to provide a seat for a valve plug such as is shown inFigure 6, and then close the drilled hole by a plug corresponding to theplug 56 when the plug shown in Figure 6 has served its purpose.

Reference may now be had more particularly to Figures 3, 4 and 5 showingthe construction of the connector 20 and of the valve plug 40. Theconnector 2D comprises an inner sleeve i12 having an enlarged centralportion t3 over which an outer sleeve il@ fits. A valve plug 6U, of aconstruc. tion such as is shown in Figures 4 and 5, fits intoa taperedseat formed at the central portion of the inner and outer sleeve.Forming a tapered seat in the connector reduces the cross-section of themetal in the connector at this point and for Ithat reason the valve plugshould be of good y conducting materialA as it serves to carry a part ofthe current. The plug l0 has a valve passageway ll which communicateswith the hollow cores of the cable and which may have a passageway i8leading from the passageway lll to the outside of the connector. 'Ihepassageway 188 may normally be plugged as by a screw plug de except whenit is desired to open communication with the oil duct in the cable, aswhen making repairs or the like. The plug ill is in addition providedwith a screw driver slot 5I) or with other means for turning the plug tothe desired position. In a similar manner the screw plug 39 is providedwith a screw driver slot or other means for turning it.

In the making of the joint, the insulation i2 of each of the twoabutting ends of the cable is rst trimmed back only about one-half ofthe length of the outer sleeve 66. Thereafter the ends of the sleeve 42'are inserted into the stranded tubular conductors IU and i0. The ends ofthe sleeve portion Al?. of the connector are tapered as indicated atlili and i5 to facilitate the insertion thereof into the strandedtubular conductors lil and l0 of the cables being connected. Thestranded conductors of the cables extend substantially to the enlargedportion 133 of the sleeve l2 and the ends of the strands are covered bythe outer sleeve ll. The cables are soldered or otherwise secured to theouter sleeve and also to the inner sleeve. The inner sleeve l2effectively prevents the entrance of solder or the like into the oilduct thus avoiding any possibility of the duct becoming plugged by anexcessive amount of solder or the like entering therein. After thecompletion of the soldering operation the insulation l2-I2 is trimmedaway in a stepped formation as shown in Figure 2.

As pointed out in our parent application of which this is a division,the oil duct within the cableis maintained full of oil under pressure,said oil seeping through the strands I of the conductor and maintainingthe insulation 'suitably impregnated. The pressure on the oil in theduct is maintained at all times in order to keep the cable full of oiland the insulation properly impregnated even during the contraction ofthe cable due to a rapid cooling thereof, and also to insure an outwardflow of oil at a fault, should one occur. It is essential that anoutward flow of oil be maintained at a fault at all times in order toprevent the ingress-of air, moisture or other impurities into the cable.Assume that a fault has occurred upon the cable system and that it hasbeen determined, by suitable means, that this fault is located in thesection of the cable indicated at 2, and further that this fault is ofsuch a-nature that it will be necessary toremove the faulty section andreplace the same byianother section, The end of the cable section 2 iscut off at a point slightly spaced from the joint indicated in Figure 2and the cut end of the cable 2 that lies adjacent the side of the jointis suitably capped to prevent an excessive loss of oil. Prior to thecapping of the section a limited amount of oil is permitted to escapefrom the cable in order to make certain that no foreign matter hascontaminated the oil that remains within the good section of the cable.The sleeve 3l is slipped back from the joint and thereafter a portion ofthe insulation 25 and 26 on the side of the defective cable is removed.'Ihis exposes the top of the ported plug 40 which is then turned 'toclose off the duct on the left-hand side thereof. The closing off ofthis plug prevents a furtherloss of oil from the cable section t to thefaulty portion of the cable section-2. Further loss of oil from the goodcable at the left of Figure 1 is now prevented except for the smallseepage of oil through the insulation at the good end. This is reducedby the insulation which still remains on the end of the good cable atthe joint thereof.

Thereafter more of the insulation is removed to permit the removal ofthe plug 40 and the substitution therefor of a plug 60 of the kind shownin Figures 6 and '7. This last mentioned plug is a temporary plug and ismade of aluminum or other material which will not readily amalgamate,solder or otherwise become bound to the copper connector or to thesolder -Which is used in conjunction therewith. This portedplug 60 has atapered conical body with a shank portion 6I which is reduced indiameter to constitute a stem portion. There is a central axialpassageway 62 extending from the larger end of the plug 60 down to thecentral part where the plug seats in the tapered hole in the connectorso that a transverse opening 63 therein may be brought intocommunication with either side of the bore in the sleeve 42 as desired.The diameter of the plug 60 is larg'er than the diameter of thetransverse bore in the inner sleeve of the connector so that a completeseat for the plug is formed, thereby in effect forming the copperconnector into a shutoff cock or shut-off and drain cock. The

ported plug is put in place in its seat in the copper connector with thedrain passageway in communication with the bore of the faulty cable end.

Now, by careful application of molten solder to the right hand end ofthe connector sleeve 46 and the exposed end thereof the conductor I0'may be unsoldered from the connector. During the unsoldering operationthe mass of oil impregnated insulation that is surrounding the left handside of the connector is in intimate contact therewith and hassufficient cooling properties to prevent, on careful handling, theunsoldering of the left hand end of the connector. Thereafter the end ofa new cable which has been suitably prepared and which may be filledwith oil is brought into position and its conductor is inserted into theconnector in the place previously occupied by the conductor IIJ'. Thejoint is then completed in a manner such as is pointed out moreparticularly in our pending parent application Serial No. 318,793 filedNovember 12, 1928, of which this application constitutes a division.Since the manner of making the joint is not a part of the inventionclaimed in the present application a further description thereof is notdeemed necessary herein, but reference may be had to the above referredto application. It may be suflicient to state that prior to thereplacement of the insulation such as 25 and 26 the temporary plug 60 isremoved and the permanent plug 40 is again inserted into the connector20, the plug 60 having been used to permit a draining of the oiladjacent the joint, which oil has been subject to a possiblecontamination. If the new cable installed was not filled with oil at thetime of installation in the duct then this plug 60 was used during theprocess of evacuation of the new length cable and the filling thereofwith oil, as pointed out in our above referred to application.

In compliance with the requirement of the patent Vstatutes we haveherein shown and described a preferred embodiment of our invention. Itis however to be understood that the invention is not limited to theprecise form herein shown, the same being merely illustrative of theinvention. What we consider new and desire to secure by Letters Patentis:

In a cable joint, the combination with adjacent lengths of cable havinginsulated hollow core conductors, said cores being full of fluid, of ahollow sleeve having a relatively thick central body and sockets onopposite sides thereof to receive and secure the conductor ends, saidbody having a transverse bore and a permanently installed metal valveplug fitting the bore which assists in carrying current between theconductors, said plug having a through passage, the ends of whichregister with the cores, and also a radial passage communicating withthe through passage and with the outside of the sleeve, and a closingmeans for the radial passage, whereby by manipulation ofthe plug and theclosing means, communication may be established between the cores andalso between the through passage and the outside of the plug and sleevewhen they are exposed, a body of insulation which covers the hollowconnecting sleeve, valve plug and the means after the plug and means areadjusted to their final positions, and an enclosing casing for thejoint.

NELSON E. BUCK. DENNEY W. iROPER.

